Experimental studies on piston slap in diesel engines (effect of gudgeon pin offset)

A series of experiments was performed on a small high-speed automobile engine which was an in-line four-cylinder IDI engine. Acceleration was measured on both sides of cylinder liner under various running conditions of the engine, that is, the rotational speed, the load and cooling water temperature. In order to evaluate the characteristics of the slap-induced vibration, acceleration recorded in the neighborhood of firing TDC was analyzed to obtain such statistical quantities as the autopower spectra, the crosspower spectra and coherence functions. It was experimentally confirmed that the gudgeon pin offset to thrust side had the effect of decreasing the vibration level, but the effect varied depending on the running condition.